Various designs of phase separation devices and settling devices are known for the separation and/or purification of liquids. Such devices are useful in many fields including water treatment, physico-chemical wastewater treatment, biological wastewater treatment, food processing, the production of pharmaceuticals and other biotechnological applications. Such reactors can include fermentation type systems in which a biomass solid is introduced to a fluidized bed system along with waste water, and fermentation is allowed to proceed. In such systems, gas can be generated and needs to be removed from the system.
One such useful phase separation apparatus is disclosed in U.S. Pat. No. 5,855,785 of Heijnen et al. The three-phase separator in that reference uses parallel plates in combination with a deflector plate to create gas-lift circulation which not only contributes to separation of the solid, liquid and gas phases, but operates to maintain biomass in the reactor longer to enhance fermentation in the lower portion of a fluidized bed apparatus having the three-phase separator at the top of the apparatus. While such device is highly effective in retaining granular biomass, it is not optimized for the clarification of suspended solids from the separator effluent. Further, while more than one such three-phase separator may be installed in a reactor, due to the space required for such units, such multiple use is limited. Further, such separators have independent and generally conically shaped settling zones, such that use of more than one such separator does not further optimize or enhance clarification of suspended solids from the separator effluent
U.S. Pat. No. 5,904,850 of Vellinga describes a settling device for fluids having solid particles, liquid and gas which has V-shaped, angled caps which are placed in the settling device on top of a large, transversely extending and inverted, single V-shaped cap which is asserted to trap some of the gas under the "V." The remaining solid, liquid and gas are passed under the obliquely angled V-shaped caps to direct gas under a further cap to an area where the gas can pass out through the top. Particulates which did not settle by gravity under the V-shaped caps are subjected to a spray head.
Reissue Pat. No. 32,597 of Pette describes an apparatus for anaerobic purification of waste water which includes an anaerobic purification area which has four after-settling compartments. Each of such compartments includes an interruption in the wall of the settling compartment for allowing water and particulate to enter the settling compartment and an opening at the bottom for allowing sludge that settles out to be directed downwardly into the reaction zone. The apparatus also has gas collection areas which may be connected to gas collection casings. Clarified liquid is removed by weirs between the compartments.
Other separation devices include those which are placed in a turbulent flow of waste water which use the undercurrent of the turbulent liquid to draw solids from quiet zones within the separation area. The quiet zones or clarification areas are formed by placing a vertically extending wall within the flow of waste water to reduce turbulence downstream of the wall and direct solid back to the lower portion of the flowing liquid. Gas is removed by bubbling up through the quiet zones. Such devices are described, for example, in U.S. Pat. Nos. 4,780,206 and 4,446,018.
While the above described devices and similar devices are useful for separation, difficulties are sometimes encountered, particularly in fluidized bed reactors, in minimizing upflow velocity to ensure a high level of separation and in providing optimal clarification of suspended solids from separated effluent As a result, there is a need in the art to improve existing phase separators, and particularly three-phase separators, to provide a device which is useful for separating phases and which can work with a fluidized bed or other upflow reactor apparatus, for example for fermentation, waste water treatment or other process to effectively remove solids or maintain solids within a reaction zone of the fluidized bed apparatus without interrupting the flow of clarified liquid. For difficult to separate media, there is a need in the art to improve separation efficiency, and, for more easily separable media, there is a need in the art to further improve such separators to allow for an overall reduction in reactor size in order to thereby reduce cost and expenses associated with the operation of larger upflow reactor apparatuses having phase separators.
Further, there is a need for a fluidized bed apparatus which has a more optimal differential flow velocity to increase the amount of solids, such as biomass, separated or retained within a reaction zone and to allow for more effective and more efficient gas and liquid separation.